In a previous publication (2) we reported, in preliminary fashion, the production of a new rapid film-changing device which would be useful for general routine radiography. At that time the unit was in the course of preparation and only an experimental model was available. Since then a practical unit has been made and we have been able to test the device in practical clinical radiography. The history of the development of rapid film-changing cassettes and their utility in vascular radiography has been adequately reviewed by Scott (3). He is responsible, to a major degree, for the first rapid film-changing device utilizing roll film, although Dotter and his associates (1) no doubt also used roll film at a very early period. Since the original contributions on this subject, numerous papers have appeared and many types of apparatus have been designed to accomplish a similar purpose. The idea, however, of using a continuous strip of film, with intermittent contact with intensifying screens and automatic separ...